Open-sight Alidades

Image: Open-sight Alidades

Detailed Description

Open-sight Alidades. This type of alidade is a straightedge with a sighting device parallel to the edge. Early alidades were simple bars with open sights on either end, while telescopic alidades were introduced in the early 1800s. The examples here of solid brass and an early plastic/wood combination. Object ID: USGS-000629, USGS-000631

Details

Image Dimensions: 2176 x 1660

Date Taken:

Location Taken: Reston, VA, US